The central goal of this project is to understand how ADHD influences processing speed, working memory, and reading comprehension in fourth- through eighth-graders. In the upper-elementary grades and beyond, students are expected to independently read (and learn from) longer and more challenging texts than at younger ages, and children with ADHD increasingly exhibit deficiencies in text comprehension even if the accuracy of their word recognition skills is unimpaired. Although past research has consistently found associations between reading disabilities (RD) and ADHD, most RD samples have included mainly children with word reading deficits (WRD) or reading disorders defined by a broad composite score (word reading accuracy and comprehension combined). In the proposed work, we instead focus on students with specific deficits in reading comprehension alone, and investigate their speed of processing and working memory (both important components of executive function), in comparison to typically developing readers. Deficits in these two areas are expected to elucidate the impact of ADHD upon reading comprehension, but potentially through different mechanisms. Further, the use of both behavioral and neurobiological (ERP, fMRI) measures in this research will permit brain-behavior relationships pertaining to these two areas to be examined. Specifically, the aims of the project are (1) to determine the behavioral and neurobiological components of processing speed, the impact of ADHD, and their contribution to reading fluency;(2) to determine the behavioral and neurobiological correlates of working memory, the impact of ADHD, and their contribution to reading comprehension;and (3) to determine the differential effects of repeated exposure and practice on automaticity and reading fluency in children with ADHD. ERP methods will be employed in Aim 1 to address "response preparation" within processing speed. fMRI methods will be employed in Aim 2 to discriminate between two memory components: short term (phonological loop/maintenance) and working (central executive/manipulation).